Teleradiology Overview Systems and Applications

Teleradiology – overview, systems and applications
Dr Sanjoy Sanyal
MBBS, MS, MSc (UK), ADPHA, ADHRD
Seychelles
Staff seminar on 27 July 2007 in Seychelles medical college

TABLE OF CONTENTS
Definition / types of teleradiology
Components
Configurations
Equipment specifications
DICOM
PACS
Applications
Telemammography
Costs
References

1. DEFINITION Teleradiology: A means of electronically transmitting patient’s radiographic images and consultative text from one location to another

1. TYPES OF TELEMEDICINE

2. COMPONENTS – Telemedicine system in general

2. COMPONENTS – Basic teleradiology system
Image sending station
Transmission network
Receiving/image review station

A. Image Sending Station
Image (film) digitizer
Network interface device (e.g. phone modem)

Image (film) digitizer
Direct digitization : No need for X-ray film and processing equipment (best)
TV camera digitizers (‘low-end’)
CCD scanner digitizers (‘mid-level’)
Laser scanner digitizers (‘high-end’)
Last three digitizers perform same function: Input X-ray film -> into scanner; analog image of film -> digital image.

Camera digitizer

Network interface device
Film digitizer has converted the image to digital format
Data is sent to the modem upon command of the equipment operator
Modem converts digital data into electrical impulses that are sent along transmission network.

B. Transmission Network
Wire
Fiberoptics
Microwave
Provided by telephone companies. This network utilizes both wire and fiberoptics
Transmission speed (and cost) closely related to transmission mode.

C. Receiving / Image Reviewing Station
1. Network interface (modem)
2. PC with storage medium (e.g. disc drive)
3. One or two TV monitors
4. Optional hard copy device printer

Receiving/Image Review Station

3. CONNECTION CONFIGURATIONS
Point-to-point connection
Local Area Network (LAN)
Wide Area Network (WAN)

A. Point-to-point connection
The basic sending and review station directly connected by a dedicated transmission network (e.g. a single wire or fiberoptic cable)

A. Point-to-point connection

B. Local Area Network (LAN)
Dedicated transmission network
Multiple sending / review stations attached
Images can be sent from several different locations within a building (or cluster of buildings) to a review station

B. Local Area Network (LAN)

C. Wide Area Network (WAN)
Many LANs interconnected - ‘super’ network
Connected by routers
Interconnected LANs represented as ‘ network cloud ’

C. Wide Area Network (WAN)

C. WAN – Telephone network
Telephone network services can be thought of as a WAN
Widely used transmission network
Advantages of using the telephone network
(1) It already exists
(2) Inner workings / complexities of network are transparent to end users
(3) Allows for readily available long / short distance connections
(4) Costs are low

Server-mediated communication

4. EQUIPMENT SPECIFICATIONS
A. Sending Station Specifications
Image resolution
Image compression
Transmission speed

Image resolution
Pixel : 512 x 512 (w x h), 1024 x 1024, or 2048 or 2048
Grey scale (density) number : 256 (8-bit depth) to 4096 (12 bit-depth)
File size:
512 x 512 x 8 bit-depth = 2,097,152 bits
1024 x 1024 x 12 bit-depth = 12,582,912 bits (6 times larger file size)

Image resolution – pixels 240 dpi 120 dpi 60 dpi 30 dpi

Image resolution – grey scale 255 grey levels / pixel 15 grey levels / pixel 5 grey levels / pixel 2 grey levels / pixel

Image compression
Compression algorithms: DCT
Lossy: JPEG (common)
Lossless: Huffman JPG; JPG-LS; RLE
Compression ratios: 2:1 to > 15:1
< 3:1 is lossless
> 3:1 is lossy

Image compression

Transmission
DS 0 (64 Kbps)
ISDN (128 Kbps)
T 1 (1.544 Mbps)
ATM: Asynchronous Transfer Mode

Transmission speed
Balance resolution, compression, and transmission speed parameters

Transmission speed

4. EQUIPMENT SPECIFICATIONS
B. Receiving/Image Review Station specifications
Modem : receiving unit modem must be > maximum speed of sending station
Computer hardware
Image enhancement software
TV monitor : Resolution, size, split-screen, brightness

Image enhancement software
Grey scale window/level
Magnification image enhancement
Colour, grey-scale mapping
Positive-negative reversal
Annotation
Minification
Edge enhancement
Image flip/rotate
Cine and histogram equalization

TV monitor
Resolution : 512 x 512 pixels to 2048 x 2048 pixels
Size : 14 – 21 inches
Split-screen : Display 2 or more different images at the same time
Brightness :
High footlamberts (greater brightness) better
Brightness differential between shades is greater
Easier for the human eye to detect

Digital display monitors
Digital display monitors : For decoding digital images for producing diagnostic quality images for reporting
Quality concerns : Whether they can match image resolution of X-ray film
Pixel content: Lack of resolution is not because of the pixel content; typically 2K pixels x 2K lines
Level of contrast : The problem is with the level of contrast - usually <100 shades of grayscale

Digital display monitors
Special techniques for correcting deficiency:
Histogram-based image transformation
Filter-based image transformation
Unsharp mask
These techniques give radiologist the ability to use ‘window’ and ‘level’ control (sort of contrast and brightness adjustments) to get adequate contrast distinction for confident reporting

Contrast-brightness control

Digital display monitor

5. DICOM
DICOM : Digital imaging & communication
ACR / NEMA standard: A set of rules
Medical scanners (US, CT, MRI, X-ray) store and exchange images in DICOM format.

5. DICOM
Allows exchange of images between digital imaging machines, computers and hospitals.
Allows teleradiology to expand from a vendor-dependent proprietary protocols and hardware to an open Internet-like system

DICOM images

DICOM viewer

6. PACS
PACS: Picture Archiving and Communication System
For distribution , storage and management of digital images and patient information.
Aiming towards filmless hospital
Web-based PACS (AMICAS ® Inc): D iagnostic-quality radiology image management services; secure image capture, distribution, workflow integration and image archiving.

PACS network

7. APPLICATIONS
Radiologists on call
Hospital physicians
Primary care / rural physicians
Tertiary subspecialty consultations
Computer-aided diagnosis (CAD)

A. Radiologists on call
On-call radiologist uses portable telerad receiving station at home
Patient images transmitted from radiology dept to radiologist’s home for immediate review

B. Hospital physicians
ICU patient images taken in Radiology Department
Quickly transmitted to ICU for review by the team responsible for that patient's care
Other involved physicians can also view images

C. Primary care / rural physicians
Primary physician can send images taken in the clinic to a radiologist in a distant location for reading and consultation

C. Primary / rural physicians

D. Tertiary super-specialist radiology consultations
A community hospital radiologist can send a complete set of images to a tertiary super-specialist (i.e. paediatric radiologist)

E. Computer-aided diagnosis
Processing / analyzing digital medical images on workstation allows computer assistance to physician for interpretation
Drawback : Increases number of negative / unnecessary biopsies without increasing incidence of positive diagnosis in mammography

E. Computer-aided diagnosis

7. TELEMAMMOGRAPHY
More women in remote areas
Mammography experts are in cities
Mammograms require special expertise
Mammogram films are 35-55 MB/film
WHY?

7. TELEMAMMOGRAPHY
High resolution is must for minute lesions
So cannot compress images
So need high-speed transmission lines
Satellite and T1 is the answer
NASA is the satellite and telemedicine expert

7. TELEMAMMOGRAPHY
STN: Satellite Telemammography Network
Ka-Band satellites: Advanced Communication Technology Satellite (ACTS)
Earth stations: T1 VSAT (Very Small Aperture Terminal)
#1: Cleveland Clinic, OH
#2: NASA Glenn Research Center @Lewis Field – ASCL
#3: University of Virginia, Charlottesville

Satellite network

NASA satellite

Earth station – NASA Glenn

Earth station – University

Radiology - reading films

9. COSTS
Low end equipment: $15,000 to $20,000
High performance systems: > $100,000
High quality sending station: ~ $35,000 to $40,000
Dual CRT receiving / viewing station: $45,000 to $55,000
( Figures are as of 1 st half of this decade )

10. REFERENCES
University of Iowa: http://www.radiology.uiowa.edu/MoreRAD/Teleradiology/Tele.html
Stephen Kinnear: http://www.scit.wlv.ac.uk/~c9581158/graphic/graphic.html
Sreedhar Raja: http://www.websamba.com/dicom4india
Chris Rorden: http://www.psychology.nottingham.ac.uk/staff/cr1/dicom.html#contrast

10. REFERENCES
NHS Purchasing and Supply Agency, UK http:// www.pasa.doh.gov.uk/dme/radiology/pacs.stm
Osman Ratib: http://www.hon.ch/Library/papers/ratib.html
NASA Glen Research Center: http://web.archive.org/web/20051002003701/ctd.lerc.nasa.gov/5610/mammography/SLSandE.html
http://www.nasa.gov/centers/glenn/news/pressrel/97_telem.html

10. REFERENCES
NASA Glen Research Center: http://www.grc.nasa.gov/WWW/RT1995/5000/5660k2.htm
SNAB: http://ctd.grc.nasa.gov/organization/branches/snab/telemedicine.html
http://www.medicalimagingmag.com/issues/articles/2006-12_07.asp
Wootton and Craig. Introduction to Telemedicine. 1999.

Teleradiology Overview Systems and Applications

by Sanjoy Sanyal

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